Such a drive unit is disclosed in EP-A-0 423 616. In order to enable flow of a sufficient quantity of cooling air through holes in the pot base, axially projecting vanes are assigned to the holes on the outside of the pot base. If such a drive unit is not equipped with a separate protective grating, then there is an increased risk of injury from the projecting vanes.
When such a drive unit is used in textile operations, there is also a risk of fluff becoming trapped on the vanes and, consequently, of the holes provided in the pot base becoming blocked as a result of the normally high incidence of fluff. As a result, sufficient cooling of the motor inside the drum is no longer ensured.
Also, GB-A-2 160 924 discloses an axial fan in which the drive motor is seated in the hub, which is designed in the form of a bell, of the axial impeller wheel. Openings are provided in the transition region of the bell base, which is connected to the motor shaft, leading to the bell wall for passage of cooling air flow therethrough. This air flow passes between the surface of the drive motor and the inside of the bell wall. The cooling air flow receives its drive energy from the pressure difference produced between the two vane sides of the axial impeller wheel.